Recently, in the field of image processing, a technology for identifying a function of an object appearing in an image has been developed. Such a technology has been applied for example to the interior design and the like. Identification of a function of an object provides a clue to knowing a design and/or a shape which is easy to use by humans. In addition, such a technology has been applied to robots making environment recognition and the like. Such robots automatically learn functions of objects and as such, the robots can gain a learning ability like that of humans. There are a variety of functions of objects depending on the object type or the object shape. Even the same object may vary in a manner of use of the object depending on the environment.
In the case of chairs as an example of the object, chairs have a variety of functions depending on the type or shape of the chair. For example, chairs 101 to 106 shown in FIG. 1 have respective shapes different from one another and respective functions different from one another. Chair 101 may be used for a person to sit, while chair 105 may be used for a person to sleep. Chair 106 may be used not only for a person to sit but also as a stool to step on. Thus, there are a variety of functions of objects depending on the object type, the object shape, the environment, and the like.
The pose assumed by a person with respect to an object varies depending on the function of the object. Namely, the function of the object is closely related to the pose assumed by the person with respect to the object. Therefore, the pose of the person with respect to the object can be effective information for identifying the function of the object. As an application of this, NPD 1 discloses a technology for estimating the function of an object by identifying the pose of a person with respect to the object. According to this technology, three-dimensional information about each joint of the person is acquired. The pose of the person with respect to the object is identified, based on a piece of pose information, to which the acquired three-dimensional information belongs, among pieces of pose information registered in advance.